1. Field of the Invention
The present invention relates to a liquid crystal display panel, and more particularly, to a seal dispenser for fabricating a liquid crystal display panel and a method for detecting a discontinuous portion of a seal pattern using the same.
2. Discussion of the Related Art
In general, a liquid crystal display panel is a display device where data signals including picture information are individually supplied to liquid crystal cells arranged in a matrix form, and the light transmittance of the liquid crystal cells is controlled to display a desired picture. Thus, the liquid crystal display device includes a liquid crystal display panel, and a driver integrated circuit (IC) for driving the liquid crystal cells. The liquid crystal cells are arranged in a unit pixel in a matrix form.
The liquid crystal display panel includes a color filter substrate and a thin film transistor array substrate facing into each other. The liquid crystal display panel further includes a liquid crystal layer between the color filter substrate and the thin film transistor array substrate.
Data lines and gate lines are formed on the thin film transistor array substrate of the liquid crystal display panel, and intersect one another at right angles, so that liquid crystal cells are defined at each intersection. The data lines transmit a data signal supplied from the data driver integrated circuit to the liquid crystal cells, and the gate lines transmit a scan signal supplied from the gate driver integrated circuit to the liquid crystal cells. At one portion of the data lines and the gate lines, a data pad and a gate pad are provided in which data signals and scan signals are applied from the data driver integrated circuit and the gate driver integrated circuit.
The gate driver integrated circuit sequentially supplies the scan signal to the gate lines so that the liquid crystal cells arranged in a matrix form may be sequentially selected line by line, and the data signal is supplied to the selected one line of the liquid crystal cells from the data driver integrated circuit.
A common electrode and a pixel electrode are formed at the inner side of the color filter substrate and the thin film transistor array substrate, and apply an electric field to the liquid crystal layer. The pixel electrode is formed at each liquid crystal cell on the thin film transistor array substrate, while the common electrode is integrally formed at the entire surface of the color filter substrate. Therefore, by controlling a voltage applied to the pixel electrode in a state where a voltage is applied to the common electrode, the light transmittance of the liquid crystal cells may be individually controlled.
In order to control the voltage applied to the pixel electrode by liquid crystal cells, a thin film transistor used as a switching device is formed at each liquid crystal cell.
Elements of the liquid crystal display device will now be described.
FIG. 1 is a plane view of a unit liquid crystal display panel having a thin film transistor array substrate and a color filter substrate according to the related art.
In FIG. 1, a liquid crystal display panel 100 includes an image display part 113 where liquid crystal cells are arranged in a matrix form, a gate pad part 114 connected to the gate lines of the image display part 113, and a data pad part 115 connected to the data lines of the image display part 113. The gate pad part 114 and the data pad part 115 are formed along the edge region of the thin film transistor array substrate 101 that does not overlap the color filter substrate 102. The gate pad part 114 supplies a scan signal from the gate driver integrated circuit to the gate lines of the image display part 113, and the data pad part 115 supplies image information from the data driver integrated circuit to the data lines of the image display part 113.
The data lines to which image information is applied and the gate lines to which a scan signal is applied intersect one another. A thin film transistor for switching the liquid crystal cells, a pixel electrode for driving the liquid crystal cells by connecting the thin film transistor, and a passivation layer formed at the entire surface to protect the electrodes and the thin film transistor are provided at the intersections.
Color filters formed at the cell regions separated by the black matrix and a common transparent electrode facing into the pixel electrode formed on the thin film transistor array substrate 101 are provided at the color filter substrate 102 of the image display part 113. A cell gap is formed by a spacer between the thin film transistor array substrate 101 and the color filter substrate 102, and the substrates are attached to each other by a seal pattern 116 formed along the outer edge of the image display part 113, thereby forming a unit liquid crystal display panel.
In fabricating a unit liquid crystal display panel, a plurality of unit liquid crystal display panels are simultaneously formed on a large-scale mother substrate. Thus, it requires a process for separating the unit liquid crystal display panels from the large-scale mother substrate by cutting and processing the mother substrate with the plurality of liquid crystal display panels formed thereon.
As for the unit liquid crystal display panel separated from the large-scale mother substrate, liquid crystal is injected through a liquid crystal injection hole to form a liquid crystal layer at the cell gap that separates the thin film transistor array substrate 101 and the color filter substrate 102, and then the liquid crystal injection hole is sealed.
As mentioned above, in order to fabricate a unit liquid crystal display panel, the processes described below are generally required. The thin film transistor array substrate 101 and the color filter substrate 102 are separately fabricated and attached to each other, such that a uniform cell gap is maintained therebetween. And, the attached substrates are cut into unit liquid crystal display panels, then a liquid crystal is injected into the cell gap of the unit liquid crystal display panel.
Especially, the process of forming the seal pattern 116 along the outer edge of the image display part 113 is required to attach the thin film transistor array substrate 101 and the color filter substrate 102. A method of forming a seal pattern according to the related art will now be described as follows.
FIGS. 2A and 2B illustrate a formation of a seal pattern by a screen printing process according to the related art.
As shown in FIGS. 2A and 2B, a patterned screen mask 206 is provided so that a seal pattern forming region is selectively exposed. A rubber squeegee 208 is provided for selectively supplying a sealant 203 to a substrate 200 through the screen mask 206 to form a seal pattern 216.
The seal pattern 216 formed on the substrate 200 is to be used for a cell gap to which liquid crystal is injected, and prevents leakage of the injected liquid crystal. Thus, the seal pattern 216 is formed along the outer edge of the image display part 213 of the substrate 200, and a liquid crystal injection hole is formed at one side of the seal pattern 216.
The screen printing method includes applying the sealant 203 on the screen mask 206 with a seal pattern forming region patterned thereon, forming the seal pattern 216 on the substrate 200 through printing with the rubber squeegee 208, drying the seal pattern 216 by evaporating a solvent contained in the seal pattern 216, and leveling the seal pattern 216.
The screen printing method is widely used due to an advantage in convenience in the process. However, it is disadvantageous in that the sealant 203 is much consumed as the sealant 203 is applied at the entire surface of the screen mask 206 and printed with the rubber squeegee 208 to form the seal pattern 216.
In addition, the screen printing method has a problem that the rubbing process of an alignment layer (not shown) formed on the substrate 200 is defective as the screen mask 206 and the substrate 200 are in contact with each other, thereby degrading a picture quality of the liquid crystal display device.
Therefore, in order to complement the shortcomings of the screen printing method, a seal dispensing method has been proposed.
FIG. 3 is a schematic view illustrating a dispensing method for forming a seal pattern according to the related art.
As shown in FIG. 3, a table 310 with a substrate 300 loaded thereon is moved in forward/backward and left/right directions. At the same time, a seal pattern 316 is formed along the outer edge of an image display part 313 of the substrate 300 by applying a pressure to a syringe 301 filled with a sealant.
In the seal dispensing method, as a sealant is selectively supplied to the region where the seal pattern 316 is to be formed, the sealant consumption may be reduced. In addition, since the syringe is not in contact with an alignment layer (not shown) of the image display part of the substrate 300, the rubbed alignment layer would not be damaged and thus a picture quality of the liquid crystal display device may be improved.
After the seal pattern 316 is formed on the substrate 300, if the substrate 300 is found defective by detecting a discontinuous portion, the substrate 300 should be discarded.
In the related art, the detection of a discontinuous portion of the seal pattern is performed by the naked eyes of an operator. That is, when the seal pattern 316 is formed on the substrate 300, the operator has to open the equipment to check whether there is a discontinuous portion of the seal pattern 316 with the naked eyes.
However, in such a case, as the equipment is opened and the operator comes in and out to the equipment, an undesirable material can be adsorbed on the substrate 300, thereby causing a deficiency in the liquid crystal display panel.
In addition, since the operator performs the detection of a discontinuous portion of the seal pattern 316 with the naked eyes, the reliability of the checking can be degraded. In other words, even if the seal pattern 316 is defective, a later process can be carried out on the substrate 300. Then, the liquid crystal display panel of a complete product should be discarded at the final detection, thereby causing a waste of material.
In addition, since the operator performs the detection of a discontinuous portion of the seal pattern 316 by the naked eyes, it takes too much time to detect the defective portion, which would degrade the productivity of a product.